A resonator can provide good loss characteristics by effectively
suppressing power losses due to an edge effect. In addition, a filter, a
duplexer, and a communication device incorporating the resonator are
formed. In the resonator, a plurality of spiral lines are disposed on a
surface of a dielectric substrate in such a manner that the inner and
outer ends of the lines are aligned respectively along an inner periphery
and an outer periphery which are centered around a central point on the
substrate so that the lines do not cross each other. With this
arrangement, the edge effect in the spiral lines is substantially
canceled, by which power losses due to the edge effect can be effectively
suppressed.
